A Dopamine Sensor Based on Pre-Concentration by Magnetic Nanoparticles
Mojtaba Bagherzadeh*a, Somayeh Ansarib, Fariborz Riahia, Anahita Farahbakhshb
a
b
Material Research School, NSTRI, Isfahan, 81465-1589, Iran.
Islamic Azad University, Shahreza Branch, Shahreza, 86145-311, Iran.
Supplementary materials
The values of saturation magnetization (Ms), remanent magnetization (Mr), and coercivity (Hc)
extracted from figure 1D were shown in Table SM1.
Table SM1. Magnetic properties of MNP
Ms/(emu•g-1)
Mr/(emu•g-1)
Hc/Oe
42
0.2≅0
2.5
MNP
Ms: saturation magnetization, Mr: remanent magnetization and Hc; coercivity.
Electrochemical behavior of DA and AA
Figure SM1 compare the CVs obtained for oxidation–reduction of AA (curves a and á), DA
(curves b and b́ ) and mixture of them (curves c and ć) at the CPE (dash line) and the
CPE/MNP (solid line) electrodes. As it can be readily understood from Fig. SM1, a
decrease in the peak current and an increase in over potential for AA oxidation, an
increase in the peak current and over potential for DA oxidation, and no peak separation
in oxidation potential of AA and DA was observed due to the presence of MNP on top of
the CPE (Fig. SM1 curve ć). Extracted parameters for electrochemical oxidation of AA
and DA at CPE and CPE/MNP electrodes are illustrated in Table SM2.
*
Corresponding author.
+983118912623.
E-mail
address:
mjmo123@yahoo.com
SM1
(M.
Bagherzadeh),
Tel/fax
number:
Fig. SM1. The cyclic voltammograms of the CPE (a, b, c) and the CPE/MNP (a`, b`, c`) obtained
in 0.1 M PBS (pH 7.0), 0.1M NaClO4 solutions containing 1 mM AA (a,a`), 1mM DA (b,
b`) and 1 mM AA and 1 mM DA (c, c`); scan rate: 100 mVs−1.
Table SM2. Electrochemical parameter for oxidation of AA and DA on CPE and
CPE/MNP electrodes, extracted from Fig. SM1.
Analyte
0.1 M DA
0.1 M AA
0.1 M DA and 0.1 M AA
Electrode
ipa/µA
CPE
87.88
CPE/MNP
165.2
CPE
64.66
CPE/MNP
41.20
CPE
137.9
CPE/MNP
307.5
*
NO: Not observed
SM2
ipc/µA
-65.72
-111.8
NO*
NO
-49.91
-125.8
Epa/mV
335.7
425.0
305.9
345.6
385.3
464.6
Epc/mV
58.00
18.30
NO
NO
97.70
67.90
Fouling effect of DA at CPE/MNP electrode
Passivation of the CPE/MNP was comparatively studied. Electrochemical oxidation
of DA at unmodified and some modified electrodes may lead to deposition of polymeric
films on the surface that decreases the electrode activity (electrode poisoning or fouling
effect) [1,2]. Thus, successive square wave voltammetric scans obtained for oxidation of
DA at the CPE/MNP electrode was recoded (Fig. SM2 (A)), and the relative responses of
ipa of DA were plotted vs. scan number (16 records) (Fig. SM2 (B)). As can be see the ipa
of DA decreased at the CPE/MNP electrode with increases in the scan number. These
results showed very unstable response for CPE/MNP electrode towards the DA oxidation,
and there is fouling property against the oxidation products at the CPE/MNP electrode.
120
100
(A)
(B)
Scan 1
100
Relative responce %
80
i/ A
80
60
Scan 16
40
60
40
20
20
0
-0.2
0
0.0
0.2
0.4
0.6
0
2
4
6
8
10
12
14
16
Number of scans
E/V (vs. Ag/AgCl)
Fig. SM2. (A) Square wave voltammetric scans obtained for oxidation of 1 mM DA in 0.1 M
PBS, pH 7.0 at the CPE/MNP electrode. (B) Relative responses of the anodic peak
current, obtained during successive recording of 16 square wave voltammograms at the
CPE/MNP modified electrode.
SM3
References:
[1]
[2]
J.A. Stamford, J.B. Justice, Anal. Chem. 68, 359A (1996).
N. J. Ke, S. S.Lu, S. H. Cheng, Electrochem. Commun. 8, 1514 (2006).
SM4